Numerical investigation of forced convection flow of a complex Bingham-Papanastasiou fluid between two concentric cylin-ders with a wavy inner wall.

This research presents a numerical investigation of the flow field and heat transfer of a Viscoplastic fluid, The Bingham-Papanastasiou model is used to examine the flow field and forced convection heat transfer of a Viscoplastic fluid between two concentric cylinders with a wavy inner surface. By focusing on this particular configuration (wavy inner cylinder shape), where the inner surface exhibits as the hot wall while the outer surface is considered as the cold wall. This investigation is numerically achieved by using the Comsol Multiphysics, which is based on the finite-volume method, employing Galerkin's method for solving the governing equations. The parameters studied in this research are expressed with the following values: r/R=1/3, Reynolds number (Re=1, 10, 50), and undulation number (nu=0, 6, 12, 24). Increasing the inertia parameter results in a higher intensity of thermal buoyancy, positively influencing heat transfer, particularly at Re=50. Furthermore, the acceleration of flow within the investigated space improves the hydrodynamic behavior, facilitating the exchange of thermal energy between the hot and cold walls. Additionally, it has been discovered that an undulating shape with a specific number of undulations (nu=6) maximizes hydrothermal performance within the investigated volume. The presence of these undulations enhances fluid mixing and disrupts the formation of stagnant regions, which leading to improved heat transfer. [ABSTRACT FROM AUTHOR]